This has been discussed a bit in other topics in the forums, so I emailed the NC GOP to find out. I asked this question--may voters registered in NC as independent or unaffiliated vote in the Republican Presidential Primary?

Here is the response--
Yes. Independent voters may choose to vote in either the Republican or Democrat primaries. However, these voters can vote in only one or the other.

Brent Woodcox
Communications Director
North Carolina Republican Party

1506 Hillsborough Street
Raleigh, NC 27605

Office: (919) 828-6423
Fax: (919) 899-3815

So in North Carolina, if you are registered as independent or unaffiliated, you may vote in EITHER the Democratic or Republican primary. Unfortunately, as things now stand, by the time NC has its primary in May, it'll be too late to matter!